Object Oriented Programming (OOP) - Interface vs Abstraction (Java/Kotlin)

[Cover Image by : Rafael de Nadai]

In the world of programming, two key concepts often come up: Interface and Abstraction. Both are fundamental to object-oriented programming (OOP) and play crucial roles in designing robust and maintainable software systems.

In this article, we'll understand the differences between Interface and Abstraction, explore various scenarios where they are used, and provide examples in both Kotlin and Java.

Key differences between Interface and Abstraction:

Now, let's explore scenarios where each concept shines.

Usage Scenarios:

Interface:

1. Plugin Architecture: Imagine we're building a text editor application that supports various plugins for different functionalities like syntax highlighting, spell checking, and auto-completion. By defining interfaces like SyntaxHighlighter, SpellChecker, and AutoCompleter, we can ensure that any plugin adhering to these interfaces seamlessly integrates with our editor.

    interface SyntaxHighlighter {
        fun highlight(text: String): String
    }
   
    // Usage
    class JavaSyntaxHighlighter : SyntaxHighlighter {
        override fun highlight(text: String): String {
            // Implement Java syntax highlighting
        }
    }
   

    interface SpellChecker {
        boolean check(String text);
    }
   
    // Usage
    class EnglishSpellChecker implements SpellChecker {
        @Override
        public boolean check(String text) {
            // Implement English spell checking
        }
    }
   

2. Testing Frameworks: When building test suites, interfaces are must. For instance, in a unit testing framework, we might define an interface Test with a method run() to execute the test cases. This allows different types of tests (e.g., unit tests, integration tests) to be executed uniformly.

    interface Test {
        fun run(): Boolean
    }
   
    // Usage
    class UnitTest : Test {
        override fun run(): Boolean {
            // Implement unit test logic
        }
    }
   

Abstraction:

1. Vehicle Simulation: Let's say we're simulating a traffic system where various vehicles operate. We could have an abstract class Vehicle with common attributes and methods such as accelerate() and brake(). Each specific vehicle type, like Car or Truck, extends this abstract class and provides its implementation.

    abstract class Vehicle {
        var speed: Double = 0.0
   
        abstract fun accelerate()
        abstract fun brake()
    }
   
    // Usage
    class Car : Vehicle() {
        override fun accelerate() {
            // Implement car acceleration
        }
   
        override fun brake() {
            // Implement car braking
        }
    }
   

    abstract class Vehicle {
        double speed = 0.0;
   
        abstract void accelerate();
        abstract void brake();
    }
   
    // Usage
    class Car extends Vehicle {
        @Override
        void accelerate() {
            // Implement car acceleration
        }
   
        @Override
        void brake() {
            // Implement car braking
        }
    }
   

2. Shape Hierarchy: Consider a scenario where we're modeling different shapes in a graphics application. We can create an abstract class Shape with methods like calculateArea() and draw(). Concrete shape classes like Circle or Rectangle extend this abstract class and provide their specific implementations.

    abstract class Shape {
        abstract fun calculateArea(): Double
        abstract fun draw()
    }
   
    // Usage
    class Circle : Shape() {
        override fun calculateArea(): Double {
            // Implement circle area calculation
        }
   
        override fun draw() {
            // Implement circle drawing
        }
    }
   

    abstract class Shape {
        abstract double calculateArea();
        abstract void draw();
    }
   
    // Usage
    class Circle extends Shape {
        @Override
        double calculateArea() {
            // Implement circle area calculation
        }
   
        @Override
        void draw() {
            // Implement circle drawing
        }
    }
   

Conclusion:

In summary,

While both Interface and Abstraction are essential concepts in OOP, they serve distinct purposes. Interfaces define contracts for classes to adhere to, facilitating polymorphism and code re-usability. On the other hand, abstractions hide implementation details and provide blueprints for sub-classes to follow, promoting code organization and maintainability.

Understanding when and how to use each concept is crucial for building scalable and maintainable software systems. By leveraging Interface and Abstraction effectively, developers can design robust, flexible, and modular applications.

That's it for today. Happy coding...